The heat dissipation of electronic devices, Integrated Circuit (IC) elements and the like is an enormous challenge to the microelectronic industry. Heat conductive greases and thermal conductive sheets have been used to prevent heat accumulation in heating elements of electronic parts typified by power transistors, ICs and CPUs. The advantage of thermal conductive greases is that they can be applied to conform to the shape of the electronic parts. However, one key issue with thermal conductive greases is that, over time, oil bleed-out may occur which contaminates other parts/components on the printed circuit. As for thermally conductive sheets, their advantage is that they do not contaminate other parts and are free from the bleeding of oil. However, they are less adhesive than greases and therefore, measures are taken to drop the hardness of the thermal-conductive sheets, thereby improving their adhesion (JP-A 1-49959 and JP-B 2623380).
Silicone rubber has been used as a thermally conductive sheet having excellent properties. When fillers, having a higher thermal conductivity than silicone for a binder, such as a silica powder, alumina, boron nitride, aluminum nitride or magnesium oxide is added, the thermal conductivity increases for the silicone rubber.
However, when it is intended to include a filler in silicone which is to be a binder, the viscosity of the compound will increase, resulting in poor flowability during the application of the material. Therefore, depending on the type and amount of filler incorporated into the silicone, the processing time to uniformly dispense the material will increase. To improve the flowability of the material, various surface-treating agents (e.g., alkoxysilane, straight-chain alkoxy oligomer and straight-chain alkoxy oligomer containing a vinyl group (JP-A 2000-1616, JP-A 2000-256558 and JP-A 2003-213133) were investigated. In spite of this, studies had shown that there were issues in the heat resistance and challenge of producing the treating agent. Also, the resultant surface-treated filler showed minimal improvement in flowability. Recent electronic parts generate a large amount of heat with the output amount thereof. A heat-discharging member is required to have a large thermal conductivity. A thermal conductive filler is required in a large amount. Such a demand is raised. Therefore, a novel way to improve the flowability of thermally conductive silicone needs to be investigated to improve the processability of the material.